We've shipped a lot of browser extensions over the years — Hide Spoilers, Markdown Editor, and plenty more. And every single time, the same speed bump appears right before submission: icons. Chrome wants a pile of sizes, the docs scatter the requirements across three pages, and the store rejects things it doesn't like with minimal explanation.
Here's the complete picture in one place — what each size is actually for — plus the workflow we use so icons take ninety seconds instead of an hour.
The core four: 16, 32, 48, 128
These go in your manifest.json under the icons key, and each one has a specific job:
- 16 × 16 — the favicon-scale icon. Shows on the extension's pages and in some context menus.
- 32 × 32 — used by Windows machines and higher-DPI situations where 16 looks like gravel.
- 48 × 48 — the
chrome://extensionsmanagement page. This is what users see when deciding whether to remove you. - 128 × 128 — installation and the Chrome Web Store. The store listing genuinely requires this one.
"icons": {
"16": "icons/16.png",
"32": "icons/32.png",
"48": "icons/48.png",
"128": "icons/128.png"
}
Technically Chrome will limp along with only 128 and scale down. Don't — downscaling at render time is how crisp logos become fuzzy thumbnails on the exact page where users decide to uninstall you.
The toolbar has its own set
The icon in the browser toolbar comes from the action key (Manifest V3), and it wants its own sizes:
"action": {
"default_icon": { "16": "icons/16.png", "24": "icons/24.png", "32": "icons/32.png" }
}
Toolbar icons render at 16 CSS pixels, so 16/24/32 covers standard and high-density displays. You'll also still see 19 × 19 and 38 × 38 in older guides — those are the legacy Manifest V2 browser_action sizes. Harmless to include, and if you're maintaining an older extension you may still need them.
One design note that outranks any size chart: toolbar icons live next to monochrome browser chrome and get very small. If your logo has fine detail, make a simplified flat version for 16–32px and save the detailed art for 128. Test against both light and dark toolbar themes — the store won't catch a black logo on a black toolbar, but your reviews will.
What the store itself wants
The Chrome Web Store listing needs the 128 × 128 icon (with about 16px of transparent padding around the actual artwork — actual mark around 96 × 96 — or it looks oversized next to every other extension), plus promotional images: a 440 × 280 small promo tile and screenshots at 1280 × 800 or 640 × 400. Icons must be PNG. Also make your icon padding transparent, not white — the store background isn't white everywhere, and light-mode-only icons look broken in dark mode.
Porting anywhere else? Edge Add-ons and Firefox AMO happily accept the same 16/32/48/128 set. A 512 × 512 master export covers you for stores and press kits that want something bigger.
The one-source-file workflow
Keep exactly one master icon — 1024 × 1024 PNG, artwork centered with breathing room — and generate everything from it, every time it changes. Never hand-edit an individual size; that's how you end up shipping an old logo at 48px and a new one at 128px (we've seen it in the wild, and yes, it looks exactly as strange as it sounds).
The generating part is why our Chrome Extension Icon Resizer exists. Drop in your 1024 master and it produces every size above — the manifest core four, the toolbar sizes, the legacy 19/38, up to 512 — with high-quality scaling, individually downloadable or as one zip, plus a ready-to-paste manifest snippet. It runs entirely in your browser, so your unreleased logo never touches a server.
Ninety seconds, every size, no Photoshop batch scripts. Save the remaining fifty-eight minutes for the actual extension.